Split shape closed loop current transducer

ABSTRACT

A current transducer having an open/closed structure of a penetration piece through which a measurement target line passes, includes: one pair of Hall devices, formed on both end gaps of an upper side portion, for sensing a current amount of the line to be measured; a feedback coil, arranged on an upper portion of the Hall devices, for canceling out a magnetic flux density of a magnet by inducing a current of a reverse direction to a current conducted in the measurement target line; a closed loop current sensing circuit for measuring a current flowing into the feedback coil; and a signal conversion circuit section for converting a current form of the measurement target line measured from the closed loop current sensing circuit into a direct current conversion signal relative to an effective value required from equipment connected to the current transducer, and outputting the direct current conversion signal.

TECHNICAL FIELD

The present invention relates to a current transducer, and moreparticularly, to a closed loop current transducer having an open/closedstructure of a penetration piece that measures a current amount of ameasurement target line in real time, converts a measured current into adirect current (DC) signal proportional to an effective value, andtransfers the DC signal.

BACKGROUND ART

The measurement of a current amount is applied at the time of measuringa consumed current amount at home or at the time of monitoring a powersupply mounted in a switchboard system of a factory.

Moreover, the current amount may be measured in real time in powerequipments of power conversion equipment, a power supply, anuninterruptible power supply system, an inverter, and the like, and themeasured current amount may be used as information for preventing theequipment from being damaged due to an abnormal current or achievinghigh efficiency. This is widely used in the fields of alternative energypower generation systems usually using a battery and a power converter,electric railway vehicles, electric automobiles, ships, and airplanes.

A conventional current measurement technology is classified as a directmeasurement method using a resistor and an indirect measurement methodusing a current transformer (CT) based on an electronic induction methodand a current sensor using a Hall device.

The resistor used in the direct measurement method is based on anon-isolation method incapable of separating power to be measured andsignal power as a method for cutting a line to be measured and directlyconnecting both ends of the measurement line, but has a problem in thatan error is added due to resistor heating occurring at high power. TheCT based on the electronic induction method serving as the indirectmeasurement method has a problem in that a measurement error is verylarge, or the measurement itself is impossible, in a non-sinusoidal waveexcept a sinusoidal waveform, a phase control wave of a powersemiconductor, a DC/ripple current waveform.

For this reason, the current sensor based on the electronic currentmeasurement method using the Hall device is recently being widely usedwhich can measure any DC/alternating current (AC) in the indirectmeasurement method.

The method using the Hall device serving as the electronic currentmeasurement method is classified into a method using an open loopcurrent sensor for measuring a magnetic force of a magnet, amplifying anoutput voltage of the Hall device serving as a magnetoelectricconversion device, and outputting the amplified voltage and a methodusing a closed loop current sensor having a feedback coil. Thetechnology of the current measurement method using the open loop currentsensor and the CT resistor is well known.

Since a signal measured by current measurement products has the sameform as that of power to be measured, there is inconvenience in that adedicated signal converter should be additionally installed to convertthe measured signal into a designated signal required for equipment whenthe equipment such as a computer, a PLC, recording equipment, displayequipment, or the like using a current measurement signal is usuallyconnected and used.

Moreover, current measurement products are inconvenient in that a lineto be measured should be disassembled upon installation and disassemblysince a measurement penetration piece is not separated or a directconnection to the line is required.

Accordingly, a user should have the electrical knowledge to use theproducts in different current waveforms of a non-sinusoidal wave, aphase controlled waveform, a DC, an AC, and the like. Otherwise, thereis a problem in that a high error occurs and the measurement isimpossible. Since a product of the dedicated signal converter is usuallyforcibly set to an approximate effective value using a mean valuecircuit, a measurement error problem occurs when a frequency or phase isdifferent. To address this problem, the current measurement productsusually use the CT for the current measurement of a commercial powersupply in a switchboard system, and the current sensor using theresistor (shunt) or Hall device for the current measurement in abattery, power conversion equipment, an electric vehicle, and the likein which a non-sinusoidal waveform and a DC waveform are present.However, this structure also has a problem in that direct mounting onthe line is required by separating the line or a penetration piece isnot open/closed. There is a problem in that the line should bedisassembled when a conventional technical product is mounted on anexisting installed line, a current measurement product should bedifferently configured in a commercial power supply, a power phasecontrol power supply, and a DC power supply, and a dedicated signalconverter should be additionally attached to convert the measured signalinto a designated signal required for equipment when the equipment suchas a computer, a PLC, recording equipment, display equipment, or thelike using a current measurement signal is usually connected and used.

DISCLOSURE Technical Problem

The present invention has been made to solve the foregoing problems withthe prior art, and therefore the present invention provides a closedloop current transducer having an open/closed structure of a penetrationpiece with high accuracy that can enable measurement in all of acommercial power supply, a power phase control power supply and a powersupply of a DC/ripple current waveform and that can neglect a gapdeviation in a separate structure.

Moreover, the present invention also provides a closed loop currenttransducer having a function of signal conversion into a form requiredfor a computer, a PLC, recording equipment, display equipment, and thelike in addition to current measurement, that is, a DC conversionfunction relative to an effective value irrespective of a DC/ACwaveform.

Technical Solution

According to an aspect of the present invention, there is provided acurrent transducer having an open/closed structure of a penetrationpiece through which a measurement target line passes. The currenttransducer includes one pair of Hall devices, formed on both end gaps ofan upper side portion, for sensing a current amount of the line to bemeasured; a feedback coil, arranged on an upper portion of the Halldevices, for canceling out a magnetic flux density of a magnet byinducing a current of a reverse direction to a current conducted in themeasurement target line; a closed loop current sensing circuit formeasuring a current flowing into the feedback coil; and a signalconversion circuit section for converting a current form of themeasurement target line measured from the closed loop current sensingcircuit into a direct current conversion signal relative to an effectivevalue required from equipment connected to the current transducer, andoutputting the direct current conversion signal.

Preferably, the signal conversion circuit section includes an effectivefunction calculation circuit for cross switching a time-divisionallydifferentiated waveform of a signal measured through the closed loopcurrent measurement circuit, calculating a direct current signalrelative to an effective value through a multi-integral method in a DSintegral circuit, and outputting the direct current signal; and a directcurrent signal amplification circuit for amplifying and outputting thedirect current signal output through the effective function calculationcircuit.

Moreover, an input/output pattern of the Hall devices is formed to passthrough a winding center of the feedback coil, and the Hall devices areformed on left and right gaps in a magnetic flux direction.

Moreover, a correction variable resistor is further formed to uniformlyadjust left and right sensitivities of the Hall devices.

Moreover, a length ratio of an upper side portion and a lower sideportion of the penetration piece is formed at 8:2 or 9:1.

Moreover, when an upper side portion and a lower side portion areseparated with reference to a hinge, the current transducer isrotatable. More preferably, when the penetration piece of the currenttransducer configures a closed loop, a fixture for coupling and fixingthe upper side portion and the lower side portion is further formed.

Moreover, an attachment hole for accommodating a nut connected to anattachment screw can be further formed to attach the current transducerto a frame or bracket.

Advantageous Effects

As set forth above, the present invention provides a closed loop currenttransducer having an open/closed structure of a penetration piece withhigh accuracy that can enable measurement in all of a commercial powersupply, a power phase control power supply and a power supply of aDC/ripple current waveform and that can neglect a gap deviation in aseparate structure.

Moreover, the present invention provides a closed loop currenttransducer having a function of signal conversion into a form requiredfor a computer, a PLC, recording equipment, display equipment, and thelike in addition to current measurement, that is, a DC conversionfunction relative to an effective value irrespective of a DC/ACwaveform.

DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing an external appearance of a closed loop currenttransducer having an open/closed structure of a penetration pieceaccording to a preferred embodiment of the present invention.

FIG. 2 is an assembly exploded view of the closed loop currenttransducer having the open/closed structure of the penetration pieceaccording to a preferred embodiment of the present invention.

FIG. 3 is an internal exploded view of the closed loop currenttransducer having the open/closed structure of the penetration pieceaccording to a preferred embodiment of the present invention.

FIG. 4 shows an example of implementing the closed loop currenttransducer having the open/closed structure of the penetration pieceaccording to a preferred embodiment of the present invention.

FIG. 5 is a circuit configuration view of the closed loop currenttransducer having the open/closed structure of the penetration pieceaccording to a preferred embodiment of the present invention.

BEST MODE

For better understanding of the present invention and the objectscapable of being achieved by implementing the present invention, theaccompanying drawings illustrating preferred embodiments of the presentinvention and contents described with reference to the accompanyingdrawings should be referenced.

Hereinafter, the present invention will be described in detail bydescribing the preferred embodiments of the present invention withreference to the accompanying drawings. The same reference numeralsdescribed in the drawings denote the same members.

FIG. 1 is a view showing an external appearance of a closed loop currenttransducer having an open/closed structure of a penetration pieceaccording to a preferred embodiment of the present invention, FIG. 2 isan assembly exploded view of the closed loop current transducer havingthe open/closed structure of the penetration piece according to apreferred embodiment of the present invention, FIG. 3 is an internalexploded view of the closed loop current transducer having theopen/closed structure of the penetration piece according to a preferredembodiment of the present invention, and FIG. 4 shows an example ofimplementing the closed loop current transducer having the open/closedstructure of the penetration piece according to a preferred embodimentof the present invention.

Referring to FIGS. 1 to 4, the closed loop current transducer having theopen/closed structure of the penetration piece of the present inventionis rotatable when an upper side portion 200 and a lower side portion 300are separated with respect to a hinge 210 to implement the open/closedstructure of a separate type penetration piece 100 in the externalappearance having a structure in which the penetration piece isopen/closed. The upper side portion 200 and the lower side portion 300have a structure for protecting internal components by coupling bodies220, 320 and covers 230, 330.

More specifically, in the upper side portion 200, the hinge 210 isarranged to form a rotation center such that the upper side portion 200and the lower side portion 300 can be supported and open/closed. Afixture 240 is formed to couple and fix the upper side portion 200 andthe lower side portion 300 such that the penetration piece 100configures the closed loop. To attach the current transducer of thepresent invention to a frame or bracket 400, an attachment hole 340 foraccommodating and supporting an attachment screw 410 and a nut 420connected thereto can be additionally formed.

An internal configuration of the current transducer of the presentinvention will be described in detail. Hall devices 250 serving asmagnets for sensing a current amount of a measurement target line 110are formed at both ends of the upper side portion 200, and avoltage-current amplification circuit 251 is formed to amplify a currentsensed from the Hall devices 250 and to configure a feedback loop suchthat a current can flow in a reverse direction to a measurement targetcurrent. More specifically, a feedback coil 252 is formed in the currenttransducer of the present invention. As the current is induced to flowin the reverse direction to the measurement target current from thefeedback coil 252, a magnetic flux density of the magnet is set to “0,”such that the magnetic flux density of a measurement point is maintainedto “0” irrespective of a large or small current amount flowing into themeasurement target line 110. At this time, the current flowing into thefeedback coil 252 is used as a current measurement output signal.Advantageously, this operation method does not depend upon thecharacteristics of a magnet 350.

Moreover, to minimize an eccentric effect in a closed loop currentsensing circuit in the penetration piece 100 upon current measurement, alength ratio of the upper side portion 200 and the lower side portion300 of the penetration piece 100 is formed at 8:2 or 9:1. A gap of themagnet 350 is formed, the feedback coil 252 is uniformly arranged at theleft and right of the upper side portion 200, and the Hall device 240 isformed on a lower end portion of the feedback coil 252, that is, a gapof the upper side portion 200.

To minimize a current measurement effect due to the earth magnetism andthe measurement depth of the closed loop current sensing circuit in thepenetration piece 100, an input/output pattern of the Hall devices 240passes through a winding center of the feedback coil 252, and the Halldevices 240 are formed on left/right gaps in a parallel structure in arelative direction, that is, a magnetic flux direction. Moreover, acorrection variable resistor (not shown) is formed to uniformly setleft/right sensitivities of the Hall devices 240, thereby adjusting asupply current of the Hall devices 240.

In order to implement the current flowing into the feedback coil 252 ina single power supply, the closed loop current sensing circuit is formedwith a power distribution circuit 253 for distributing supply power toboth sides and a current-voltage conversion resistor 254 for convertinga current measurement output signal current into a voltage.

Moreover, the current transducer of the present invention includes asignal conversion circuit section having an effective functioncalculation circuit 255 for a non-sinusoidal wave for converting ameasurement signal having the same form as the current of themeasurement target line 110 measured from the closed loop currentsensing circuit into a DC conversion signal relative to an effectivevalue corresponding to a special signal required by equipment such as acomputer, a PLC, recording equipment, display equipment, or the like toprovide the DC conversion signal, and a DC signal amplification circuit256 for amplification to a DC output signal relative to a calculatedeffective value.

The current transducer of the present invention has the externalappearance of the structure in which the penetration piece 100 isopen/closed, and can implement current measurement and conversionfunctions in one product by integrating the closed loop currentmeasurement circuit having the power distribution circuit 253 and thecurrent-voltage conversion resistor 254 and the signal conversioncircuit section having the effective function calculation circuit 255for the non-sinusoidal wave and the DC signal amplification circuit 256.At the time of mounting on the existing installed measurement targetline 110, the penetration piece 100 of the current transducer can beeasily installed to be open/closed without disassembling the installedline.

FIG. 5 is a circuit configuration view of the closed loop currenttransducer having the open/closed structure of the penetration pieceaccording to a preferred embodiment of the present invention.

Referring to FIG. 5, the closed loop current measurement circuit havingthe power distribution circuit 253 and the current-voltage conversionresistor 254 forms an electromagnetic field proportional to a currentamount when the current flows into the measurement target line 110through the penetration piece 100. The electromagnetic field forms amagnetic field by magnetizing the magnet 350. A magnetic force is formedby a generated magnetic flux density on the gap of the magnet 350, andmagnetoelectric conversion is achieved through the Hall devices 250.

A conversion voltage generated through the magnetoelectric conversion ofthe Hall devices 250 is directly transferred to the voltage-currentamplification circuit 251 of the infinite theory, and thevoltage-current amplification circuit 251 transfers a current componentof an instantaneous amplification output to the feedback coil 252.

The feedback coil 252 is wound in a reverse direction to a current flowof the measurement target line 110, such that the current flowsthereinto. At this time, the magnetic flux density of the magnet 350 isinstantaneously directed to “0.” When the measurement target line 110 isset to “1,” the current flows into the feedback coil 252 at a ratio ofXN turns. The current flowing into the feedback coil 252 forms a currentamount at the magnetic flux density of “0.” The closed loop is formedusing the current flowing into the feedback coil 252 as a measurementcurrent signal, such that an amount of current flowing into themeasurement target line can be measured. This is because the closed loopcurrent sensing circuit is formed by implementing a double power supplyon a single power supply when the power distribution circuit 253 forms avirtual power reference point such that a current signal flowing intothe feedback coil 252 is incoming/outgoing through the current-voltageconversion resistor 254.

The signal conversion section having the effective function calculationcircuit 255 for the non-sinusoidal wave and the current signalamplification circuit 256 is a circuit for converting an output signalmeasured by the closed loop current sensing circuit into a target outputsignal, and converts an output signal having the same form as thecurrent of the measurement target line 110 measured by the closed loopcurrent sensing circuit into a DC conversion signal corresponding to aspecial signal required by equipment such as a computer, a PLC,recording equipment, display equipment, or the like to provide the DCconversion signal. More specifically, the current measurement signalgenerated in the current-voltage conversion resistor 254 of the closedloop current sensing circuit is output by cross switching a waveformtime-divisionally differentiated through the effective functioncalculation circuit 255 and calculating a DC signal relative to aneffective value through a multi-integral method in a DS integralcircuit. A signal converted into the DC through the DC signalamplification circuit 256 is amplified to DC 4˜20 mA or DC 1˜5 Vcorresponding to an output signal form required by the connectedequipment and the amplified signal is output.

In order to measure a current without measurement error in the separatetype of current transducer of the present invention, it is important toavoid the effect of a gap of the magnet 350 occurring in the separatestructure of the upper side portion 200 and the lower side portion 300.This can be realized only in the closed loop of which the magnetic fluxdensity is directed to “0.” This is because a gain is determined by thenumber of turns of the feedback coil 252 proportional to a currentamount to be measured.

When the current transducer of the present invention is used, thecurrent measurement process does not depend upon the characteristics ofthe magnet 252, such that frequency characteristics can be significantlyimproved and a frequency bandwidth can be maximally extended accordingto magnet performance and semiconductor performance of an electroniccircuit to be applied. Moreover, a measurement waveform is possible in arange from a DC to an AC of several hundreds kHz. Since the measurementwaveform is not limited and a DC conversion circuit relative to a trueeffective value is provided, a special signal transducer is not requiredand therefore a unified current transducer having the above-describedelectrical characteristics can be effectively provided.

While the present invention has been shown and described with referenceto certain embodiments, it will be understood by those skilled in theart that various modifications may be made therein without departingfrom the spirit and scope of the present invention as defined by theappended claims and their equivalents.

1. A current transducer having an open/closed structure of a penetrationpiece through which a measurement target line passes, comprising: onepair of Hall devices, formed on both end gaps of an upper side portion,for sensing a current amount of the line to be measured; a feedbackcoil, arranged on an upper portion of the Hall devices, for cancelingout a magnetic flux density of a magnet by inducing a current of areverse direction to a current conducted in the measurement target line;a closed loop current sensing circuit for measuring a current flowinginto the feedback coil; and a signal conversion circuit section forconverting a current form of the measurement target line measured fromthe closed loop current sensing circuit into a direct current conversionsignal relative to an effective value required from equipment connectedto the current transducer, and outputting the direct current conversionsignal.
 2. The current transducer having the open/closed structure ofthe penetration piece according to claim 1, wherein the signalconversion circuit section includes: an effective function calculationcircuit for cross switching a time-divisionally differentiated waveformof a signal measured through the closed loop current measurementcircuit, calculating a direct current signal relative to an effectivevalue through a multi-integral method in a DS integral circuit, andoutputting the direct current signal; and a direct current signalamplification circuit for amplifying and outputting the direct currentsignal output through the effective function calculation circuit.
 3. Thecurrent transducer having the open/closed structure of the penetrationpiece according to claim 1, wherein an input/output pattern of the Halldevices is formed to pass through a winding center of the feedback coil,and the Hall devices are formed on left and right gaps in a magneticflux direction.
 4. The current transducer having the open/closedstructure of the penetration piece according to claim 1, furthercomprising: a correction variable resistor for uniformly adjusting leftand right sensitivities of the Hall devices.
 5. The current transducerhaving the open/closed structure of the penetration piece according toclaim 1, wherein a length ratio of an upper side portion and a lowerside portion of the penetration piece is formed at 8:2 or 9:1.
 6. Thecurrent transducer having the open/closed structure of the penetrationpiece according to claim 1, wherein when an upper side portion and alower side portion are separated with reference to a hinge, the currenttransducer is rotatable.
 7. The current transducer having theopen/closed structure of the penetration piece according to claim 6,wherein when the penetration piece of the current transducer configuresa closed loop, a fixture for coupling and fixing the upper side portionand the lower side portion is further formed.
 8. The current transducerhaving the open/closed structure of the penetration piece according toclaim 1, wherein an attachment hole for accommodating a nut connected toan attachment screw is further formed to attach the current transducerto a frame or bracket.